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Re: Best rechargeable "D" cell

Just speaking out loud as I'm further learning / understanding this stuff:

In a regulated light like the TK70, it needs 9.6 amps I think. So with 4 D cells that is 2.4 amps per D cell. I think it needs like 4.8v so each cell is providing its correct 1.2v. But with under that heavy load, if a cell is not capable of producing enought volts per amperage drain, it will cause the light to kick down from turbo to high (the light's driver does the kick down as soon as not enough volts from the battery pack is not avaiable anymore.

Re: Best rechargeable "D" cell

Originally Posted by hank

357mag1, can you describe exactly how you're testing D cells with the Turnigy?
I've got an Accucel-6 now and can probably set it up the same way you're doing and compare.
I've only used it with single cells, never with more than one at a time.

I was wondering if the Accucel-6 can handle multiple batteries if set up properly to do effectively the same charge and discharge as the Maha D-cell charger others are using.

The Accucel-6 has a 1A max discharge vs Accucel 8150 5A but I could be wrong. I concur that my 16 Marrsinc blue D cells have never exceeded 9500ma averaging closer to 8600ma. My 8 premium white Tenergy cells avg 10,500ma. Biggest bang for the buck Marrs blue Ds. On Big Chelis endorsement I purchased the Tenergy Ds and can attest to their high draw low sag capabilities. My PT120 green will pull a 25A+ with hot off the charger 4 D cells via direct drive.

Re: Best rechargeable "D" cell

I did that with white cells. Have pulled 20A+ with blue cells with in an hour off the charger. Actually these numbers might be conservative. IIRC read that Lambda has pulled 30A from these cells in 4D configuration.

Re: Best rechargeable "D" cell

Originally Posted by CyberCT

357mag1, I appreciate your feedback and help.

I'm learning, and think I finally have an idea of what's going on here. Confirm I do or correct me where I don't. I'm still learning and have picked up bits & pieces over the last two years but think I got it:

There are different mah values:

1) Charge capacity of a battery is how much charge it can take from the charger in mah, which will usually be the the highest capacity of the battery.

2) Discharge capacity, which is how much mah a battery can produce for a load. That value will be lower than the charge capacity. Now, for the discharge capacity, the discharge capacity mah values can vary depending on the load or rate of discharge. Let's use an eneloop. The charge capacity might be 2,000 mah. Under a .2 amp load, the battery might produce 1,950 mah. Under .5 amp load, the battery might produce 1,850 mah. Under a 1 amp load, the battery might produce 1,700 mah.

3) The amount of voltage a battery can supply under load. A NIMH battery such as an eneloop is rated at 1.2v. now let's say there is a .5 amp load on the battery. If it produces about 1.15v and 1,850 mah that is better than another AA battery that produces, at .5 amps load, 1.05v but say 1,950 mah? I'm still a little confused about this a little.

Would it be safe to say that a battery with a stated capacity that matches closely its discharge capacity is a good quality battery? Like if a D battery can take 10,000 mah from a charger, but as soon as a load of say 1 amp hits the battery it drops to 8,000 mah capacity, that cell isn't as high quality as a cell that is stated at 9,000 mah capacity but produces 9,000 capacity under load?

When you mentioned that your blue Tenergy cells were around 7,000 mah capacity, you were doing a discharge test of each at what, 4 amps? If you did a 1 amp discharge test should you expect a capacity of more like 9,000 mah?

Just curious, what capacity did the Eneloops show on your C9000 vs the Rayovacs, when you did the discharge?
And which of those two chargers you mentioned do you like better?

CyberCT,

You pretty much have a handle on it with the exception of the amount of mah a battery takes when charging. Lesser quality batteries always seem to take more mah during charge than they can ever deliver under a load. I think it may have something to do with lesser quality cells being harder for the charger to find a termination point but don't really know.

My discharge tests were at 3 and 5amps. All the batteries were done at 3 and about half at 5. I didn't keep doing the 5amp test because there did not appear to be any difference in capacity between the rates. I haven't seen where quality nimh cells vary much in capacity if the load is kept reasonable for the cell.

Try this test with your C9000 and two Eneloops of similiar capacity. Discharge one at 1amp and one at 200ma and see how much difference in capacity you get. I wager little to none. At least that was my experience.

The Eneloop and Rayovac AAA had been setting about 3-4 months. I didn't write it down but going from memory the Eneloops were all 640 - almost 700mah and the Rayovacs averaged around 540mah. The Eneloops had a significantly higher voltage during the discharge cycle.

I like the Triton2 EQ better but it is a $170 charger compared to $46 for the Accucell. If I were to do it again I would buy the FMA PowerLab 8 v2 from Progressiverc. Buying quality only hurts once.

Re: Best rechargeable "D" cell

Originally Posted by CyberCT

Just speaking out loud as I'm further learning / understanding this stuff:

In a regulated light like the TK70, it needs 9.6 amps I think. So with 4 D cells that is 2.4 amps per D cell. I think it needs like 4.8v so each cell is providing its correct 1.2v. But with under that heavy load, if a cell is not capable of producing enought volts per amperage drain, it will cause the light to kick down from turbo to high (the light's driver does the kick down as soon as not enough volts from the battery pack is not avaiable anymore.

9.6 amps per cell in a 4 cell configuration ? theoretically if you had 3 cells on the tk70, amperage goes up 33% under load to supply the watts needed? to around 12.8 amps? Or are my calculations a** backwards?

Re: Best rechargeable "D" cell

Originally Posted by chewy78

9.6 amps per cell in a 4 cell configuration ? theoretically if you had 3 cells on the tk70, amperage goes up 33% under load to supply the watts needed? to around 12.8 amps? Or are my calculations a** backwards?

No, it's 9.6 amps total. So divide that by 3 for 3 cells (3.2a), and 4 for 4 cells (2.4a).

Re: Best rechargeable "D" cell

Originally Posted by 357mag1

My discharge tests were at 3 and 5amps. All the batteries were done at 3 and about half at 5. I didn't keep doing the 5amp test because there did not appear to be any difference in capacity between the rates.

At the moment I only have my C9000. Once I have my rig set up so I can discharge my Tenergy Ds at 1 amp max, I will do a few recharge, and then discharge tests per cell. Then I will battery match the best four, the 2nd best 4, the 3rd best 4, and then the last worst 4. So these results are based on a 1 amp discharge. If I could do a 3 amp discharge, should I expect the matched batteries to perform comparitevly? Like should I expect the best 4 performing under a 1 amp draw to perform the best under a 3 amp draw? Or would it completely change? Like one of the best at 1 amp draw is 1 of the worst under a 3 amp draw.

Re: Best rechargeable "D" cell

Originally Posted by chewy78

9.6 amps per cell in a 4 cell configuration ? theoretically if you had 3 cells on the tk70, amperage goes up 33% under load to supply the watts needed? to around 12.8 amps? Or are my calculations a** backwards?

The tk70 uses somehwere between 30 to 35watts on turbo. just divide that number by the total voltage of the cells to see what the amps needs to be. When the 4 cells are fresh it uses about 7.2 amps.

Re: Best rechargeable "D" cell

Originally Posted by CyberCT

Just speaking out loud as I'm further learning / understanding this stuff:

In a regulated light like the TK70, it needs 9.6 amps I think. So with 4 D cells that is 2.4 amps per D cell. I think it needs like 4.8v so each cell is providing its correct 1.2v. But with under that heavy load, if a cell is not capable of producing enought volts per amperage drain, it will cause the light to kick down from turbo to high (the light's driver does the kick down as soon as not enough volts from the battery pack is not avaiable anymore.

CyberCT,

Current in series is common so whatever current is at the tailcap all cells are felling that draw. In the case of the TK70 all three cells are feeling the 9.84amp draw (from my test). With 4 cells it drops to 6.25amps and again each cell has that current drawn through it.

Re: Best rechargeable "D" cell

Originally Posted by CyberCT

ok thanks for that clarification. I wonder why the new TK70 draws more from the cells than the old one?

The newer one appears slightly brighter on Turbo. It might just be variance in driver boards and LEDs. After 30+ years in the field nothing in electronics comes out exactly the same. Kind of like snow flakes.

I have a chart inside an Open Office (Open Source, not Microsoft) I could send you via Email. It list the current draw for both TK70s and my TK60 using various battery configurations. I've tried posting it on here but have not had any luck (Format gets messed up).

Re: Best rechargeable "D" cell

Originally Posted by 357mag1

CyberCT,

Current in series is common so whatever current is at the tailcap all cells are felling that draw. In the case of the TK70 all three cells are feeling the 9.84amp draw (from my test). With 4 cells it drops to 6.25amps and again each cell has that current drawn through it.

My Newer TK70 draws 10.7amps on 3 cells and 7.2amps with 4 cells.

Do you recall what the serial number variance is on the old vs. new lights? Just trying to get an idea of what newer would mean. Neither of these are a TK70S right?

Re: Best rechargeable "D" cell

Do you recall what the serial number variance is on the old vs. new lights? Just trying to get an idea of what newer would mean. Neither of these are a TK70S right?

Thanks,
JD

Both of my TK70s run on D cells. I believe the TK70S uses Lithium cells by design but don't know.
My original TK70 is serial F46H9600215 and the newer one is F46H9C00505.

I believe there was a circuitry change in there somewhere but have no idea when or where in the serial numbers it came about.

Besides drawing more current and looking slightly brighter the newer version also has this difference. No matter what mode it is in when you unscrew the tailcap the new light comes on in low when you first put fresh batteries in and fire it up. I used to think the older light came on in Turbo after a battery change but that was just the mode I had it in most of the time. It actually remembers the last mode used and comes on in that mode after changing out batteries or loosening and securing the tailcap.

So the older light will remember the last selected mode when changing batteries and the new always starts back at low.

My two TK70s are the only ones I've ever seen or handled so maybe one of my lights has issues but I don't think so. They appear to have slightly different circuitry. Maybe one of our Fenix distributors could shed some light on any TK70 circuitry changes.

Re: Best rechargeable "D" cell

Originally Posted by CyberCT

Just speaking out loud as I'm further learning / understanding this stuff:

In a regulated light like the TK70, it needs 9.6 amps I think. So with 4 D cells that is 2.4 amps per D cell. I think it needs like 4.8v so each cell is providing its correct 1.2v. But with under that heavy load, if a cell is not capable of producing enought volts per amperage drain, it will cause the light to kick down from turbo to high (the light's driver does the kick down as soon as not enough volts from the battery pack is not avaiable anymore.

Re: Best rechargeable "D" cell

Both of my TK70s run on D cells. I believe the TK70S uses Lithium cells by design but don't know.
My original TK70 is serial F46H9600215 and the newer one is F46H9C00505.

I believe there was a circuitry change in there somewhere but have no idea when or where in the serial numbers it came about.

Besides drawing more current and looking slightly brighter the newer version also has this difference. No matter what mode it is in when you unscrew the tailcap the new light comes on in low when you first put fresh batteries in and fire it up. I used to think the older light came on in Turbo after a battery change but that was just the mode I had it in most of the time. It actually remembers the last mode used and comes on in that mode after changing out batteries or loosening and securing the tailcap.

So the older light will remember the last selected mode when changing batteries and the new always starts back at low.

My two TK70s are the only ones I've ever seen or handled so maybe one of my lights has issues but I don't think so. They appear to have slightly different circuitry. Maybe one of our Fenix distributors could shed some light on any TK70 circuitry changes.

Hope that info helps.

This is very interesting. My TK70 acts like your old one and has the same preface of the serial number. I suppose i have one of the old ones. One thing is that if i leave the batteries out long enough it will default back to low. But if i just undo the tailcap and then reconnect, it will go back to the last used mode. This is a bummer. Kinda wish i had a new one.

Re: Best rechargeable "D" cell

Hmm I'll have to do that test when I get mine in the mail (hopefully tomorrow). I think shortly after the TK70 was released people started complaing about the light only selecting low mode or some issue. So maybe a flood of returns caused Fenix to do a quick and quiet redesign?

Re: Best rechargeable "D" cell

Originally Posted by JudasD

This is very interesting. My TK70 acts like your old one and has the same preface of the serial number. I suppose i have one of the old ones. One thing is that if i leave the batteries out long enough it will default back to low. But if i just undo the tailcap and then reconnect, it will go back to the last used mode. This is a bummer. Kinda wish i had a new one.

JD

JD,
I'm trying that test on my older one. I will leave the cap off for a while and see if it drops back to low mode.

It just takes money to get a new one!!!

If you would be interested I just found a place to get new in the box Fenix lights at awesome prices. The guy is stateside and awesome to work with. Wish I would have known about this guy before CyberCT purchased his TK70. Probably could have saved him some cash.

Re: Best rechargeable "D" cell

Originally Posted by 357mag1

JD,
I'm trying that test on my older one. I will leave the cap off for a while and see if it drops back to low mode.

It just takes money to get a new one!!!

If you would be interested I just found a place to get new in the box Fenix lights at awesome prices. The guy is stateside and awesome to work with. Wish I would have known about this guy before CyberCT purchased his TK70. Probably could have saved him some cash.

357mag - i'm interested in that link...could you post it or send it to me in a 'pm'?...
i'm very new to this flashlight obsession thing but caught the bug and set my sights on the tk70...plan to purchase one within 2 weeks...was going to buy from battery junction...if i can get a new tk70 for better price i'm interested of course...

also, getting somewhat confused by all these posts here re-best rechargeable d cells...there are several different opinions by different postees on this thread....i read some strongly stated opinion and thought i have the answer, only to see it shot down by another opinion...crap....

357mag, since you've evidently done a lot of long term d-cell tests AND own a couple of tk70s i'm willing to stake my choice on your recommendation man....
along with the tk70, i'm planning to buy the maha c808m charger so i can charge d cells for the tk70 AND use 4 d cell batteries in that light, not alternative adapters, etc...length and weight penalty notwithstanding.....which 'top 2' nimh lsd rechargeable d-cells are recommended after all, considering the longest run time on turbo mode and extended period of being inside the flashlight [i.e. slow discharge]??...
thanks - jerzy...

Last edited by LIGAF; 02-18-2012 at 08:35 AM.
Reason: missed a couple of details...

Re: Best rechargeable "D" cell

Originally Posted by LIGAF

357mag - i'm interested in that link...could you post it or send it to me in a 'pm'?...
i'm very new to this flashlight obsession thing but caught the bug and set my sights on the tk70...plan to purchase one within 2 weeks...was going to buy from battery junction...if i can get a new tk70 for better price i'm interested of course...

also, getting somewhat confused by all these posts here re-best rechargeable d cells...there are several different opinions by different postees on this thread....i read some strongly stated opinion and thought i have the answer, only to see it shot down by another opinion...crap....

357mag, since you've evidently done a lot of long term d-cell tests AND own a couple of tk70s i'm willing to stake my choice on your recommendation man....
along with the tk70, i'm planning to buy the maha c808m charger so i can charge d cells for the tk70 AND use 4 d cell batteries in that light, not alternative adapters, etc...length and weight penalty notwithstanding.....which 'top 2' nimh lsd rechargeable d-cells are recommended after all, considering the longest run time on turbo mode and extended period of being inside the flashlight [i.e. slow discharge]??...
thanks - jerzy...

I don't claim to be an expert and can only comment on the cells I've tested. For LSD I've tested the AccuEvolution, Imedion and Tenergy Centura. Though one of the most economical the Centura easily best the other two.

If it were me I would not purchase LSD D cells unless I planned to put them into a light and let it set for at least 6 months and that light had to work when I picked it up!!!

Otherwise the best Nimh D cell on the market that I've tested is the Tenergy Premium. I would purchase them from All-battery.com but use their Ebay store. The batteries are listed cheaper there and shipping is less.

The Premiums I've tested after setting for 2 months still have more capacity left than the best LSD cells do fresh off the charger. The fact the Premiums still maintain a higher voltage under load even though their resting voltage is lower makes them the hands down winner for me.

Battery Junction would not be on my list of Merchants to buy anything from ever again.

Re: Best rechargeable "D" cell

Hello CyberCT,

Originally Posted by CyberCT

357mag1, I appreciate your feedback and help.

I'm learning, and think I finally have an idea of what's going on here. Confirm I do or correct me where I don't. I'm still learning and have picked up bits & pieces over the last two years but think I got it:

There are different mah values:

1) Charge capacity of a battery is how much charge it can take from the charger in mah, which will usually be the the highest capacity of the battery.

2) Discharge capacity, which is how much mah a battery can produce for a load. That value will be lower than the charge capacity. Now, for the discharge capacity, the discharge capacity mah values can vary depending on the load or rate of discharge. Let's use an eneloop. The charge capacity might be 2,000 mah. Under a .2 amp load, the battery might produce 1,950 mah. Under .5 amp load, the battery might produce 1,850 mah. Under a 1 amp load, the battery might produce 1,700 mah.

3) The amount of voltage a battery can supply under load. A NIMH battery such as an eneloop is rated at 1.2v. now let's say there is a .5 amp load on the battery. If it produces about 1.15v and 1,850 mah that is better than another AA battery that produces, at .5 amps load, 1.05v but say 1,950 mah? I'm still a little confused about this a little.

Would it be safe to say that a battery with a stated capacity that matches closely its discharge capacity is a good quality battery? Like if a D battery can take 10,000 mah from a charger, but as soon as a load of say 1 amp hits the battery it drops to 8,000 mah capacity, that cell isn't as high quality as a cell that is stated at 9,000 mah capacity but produces 9,000 capacity under load?

When you mentioned that your blue Tenergy cells were around 7,000 mah capacity, you were doing a discharge test of each at what, 4 amps? If you did a 1 amp discharge test should you expect a capacity of more like 9,000 mah?

Just curious, what capacity did the Eneloops show on your C9000 vs the Rayovacs, when you did the discharge?
And which of those two chargers you mentioned do you like better?

A slight correction... Or perhaps a perspective review.

The mAh of a cell refers to its capacity. This capacity is determined during discharge. The discharge capacity is the "official" number. This number is dependent upon a number of things including the discharge rate. When a cell is labeled with a capacity, it was supposed to have been tested according to standard methods that include a standard charge followed by a standard discharge.

In battery testing a standard charge involves charging the cell at a 0.1C charge rate for 16 hours. Following a rest period the cell is then subjected to a standard discharge. The standard discharge rate is 0.2C. This works out to 16 hours of charging, about 1 - 2 hours of rest, and about 5 hours of discharge.

While battery manufacturers test according to these standards, there is no rule that the person making up the label for the cell has to read the results, and there is varying "truth in labeling."

This is why we do testing. If the label says 10000 mAh, and the cell only is capable of delivering 6000 mAh, we know that the label was optimistic. Some manufacturers (Sanyo Eneloop for example) give a minimum capacity for their cells. In this particular case, the Eneloop cells actually test out very close to what they are labeled at.

The amount of charge you put into the cell is important, but it tells you nothing about the capacity of the cell. It does tell you how well the termination method used by the charger works. For example, the amount of charge that goes into a cell depends upon charge rate. When charging at 0.1C, if everything were perfect the cell should be fully charged in 10 hours. However, due to inefficiencies a full charge actually takes 16 hours. If you raise the charge rate to 1.0C, you expect the total charge going into the cell to be about 105 - 110%. If your charger misses its termination, the cell gets hot and the charge number raises much higher. This can actually damage the cell and produce a lower discharge capacity.

So, if you see a cell that has a higher charging capacity it could mean that something is going on with either the charger or the cell and it has been overcharged due to the charge termination signal being missed.

You have a good grasp on the discharge capacity. This is the actual capacity of the cell. The standard load used to determine the capacity is a 5 hour discharge or 0.2C. I like to see how close the labeled capacity is to the cells actual capacity, and then to see what the capacity of the cell is under the loads I plan to use.

The voltage under load varies with the load. The "nominal" voltage of 1.2 volts comes from the voltage seen during the standard discharge. As a cell ages, its ability to hold voltage under load is reduced. This reduced voltage also results in reduced capacity. When using cells in a multi cell application you are better off if the cells are matched to each other. Matching is done on both capacity and voltage under load. Matched cells help reduce the problem of cell reversal when the battery pack is at the end of the discharge cycle.

It is rare to have a cell match its labeled capacity. The exception to this is if the cell has a discharge sheet from the battery manufacturer. For example with AA cells the sheet from Sanyo on the Eneloop cells very closely matches the labeled capacity of the cell. GP cells are a little off on labeling, but the sheets are closer to the actual capacity. The GP 2700 mAh cells while having 2700 mAh on their label have data sheets that show the capacity is closer to 2550 mAh. When you test these cells you find that they come in close to the data sheet capacities. The label in this case is optimistic.

Capacity under load is a good way to start looking at the quality of a cell, but the story goes on from there. Voltage under load is another consideration, as are the number of charge/discharge cycles the cell can handle. I have had some cells that had good capacity and good voltage under load, but they only lasted 20 cycles and then everything tanked and they turned into crap cells. Other cells with less capacity were still going strong after 100 charge/discharge cycles, and in my opinion they were higher quality.

This should help you understand a little more about battery testing and how to interpret the numbers you observe.

Tom

Behind every Great man there's always a woman rolling her eyes...

Most batteries don't die - they are tortured to near death, then murdered...

Re: Best rechargeable "D" cell

Originally Posted by 357mag1

I don't claim to be an expert and can only comment on the cells I've tested. For LSD I've tested the AccuEvolution, Imedion and Tenergy Centura. Though one of the most economical the Centura easily best the other two.

If it were me I would not purchase LSD D cells unless I planned to put them into a light and let it set for at least 6 months and that light had to work when I picked it up!!!

Otherwise the best Nimh D cell on the market that I've tested is the Tenergy Premium. I would purchase them from All-battery.com but use their Ebay store. The batteries are listed cheaper there and shipping is less.

The Premiums I've tested after setting for 2 months still have more capacity left than the best LSD cells do fresh off the charger. The fact the Premiums still maintain a higher voltage under load even though their resting voltage is lower makes them the hands down winner for me.

Battery Junction would not be on my list of Merchants to buy anything from ever again.

Re: Best rechargeable "D" cell

Well my TK70 did not arrive today either, so I said screw it and put my first half of Tenergy cells in the "soft" "conditioning" mode of my 808M. If it takes 60 hours to complete, they should be ready Monday night. My TK70 should be at my doorstep earlier that night when I get home so it's no big deal. I'm going to do some runtime tests to turbo with the 3 cell tube, and the 4 cell tube. Seeing how these batteries are hit or miss, I'll to the same test once I have rigged up my C9000 to discharge my D cells and give an mah value, and then do cell matching. I'm thinking of doing 3 tests per cell and I'll take the average. I have found from testing my AA and AAA batteries that sometimes all 4 bays have a lower reading, and the next time they have a higher reading from the same cells, same cycling mode. Not too much of a difference but an average is the best way to go I think.

SO is the C9000 showing the voltage of the cells when the discharge stopped? Or how they held up?

Unfortunately the C9000 doesn't not show average voltage for the discharge cycle. You are just seeing the resting voltage at that moment after discharge. Depending on how long you wait it will continue to climb until it stops around the 1.2 volt mark.

Try discharging them at the same time push the "Slot" button at different times during the discharge cycle (5 minutes, 10, 20, 30, 45, ect). Each slot will rotate through the voltage of the cell, it takes about 10 seconds for each slot. Write those numbers down and compare them. You will have a fair idea which batteries maintain the higher voltage.

My Triton2 EQ provides the average voltage during discharge something I wish the C9000 did.

Re: Best rechargeable "D" cell

My low capacity Blue Tenergy D cell completed the "Conditioning" cycle on the MAHA 808. I let it rest an hour and it read the lowest capacity yet, 5862mah when discharged at 3 amps. Previously it has read between 5899 and 5929mah.

I was going to call it a weak cell but it is really just lower in capacity as it maitains voltage under load with the best cells. I wish I had annotated which cells were the lowest coming out of the pack. I'm wondering if they are the lower capacity cells.